First thing I’ll start experimenting. Remember we’re back to the 9090DB Tuner Board.
Sansui 9090 W/O Working Tuner/Dial Lamps/Meters
- Thread starter JJCalvillo
- Start date
Had to step away after I posted the voltages. Sold a friend’s 2230 and the guy was coming over to listen to it
Yep that diagram with the orange blobs is from the DB service manual.
Pulled one leg of R61 and we have FM at normal levels, AM as well. 
No clue why this is the case.
Do I completely remove R61 and call it a day?
Only thing left is no Stereo lamp lighting, so not sure if we're not getting stereo or it's just a dead lamp. Will test it.
Oh, and AM works but the signal strength meter is pegged right all the time, works normally in FM. Tuning meter works on AM too, is that normal?
No clue why this is the case.
Do I completely remove R61 and call it a day?
Only thing left is no Stereo lamp lighting, so not sure if we're not getting stereo or it's just a dead lamp. Will test it.
Oh, and AM works but the signal strength meter is pegged right all the time, works normally in FM. Tuning meter works on AM too, is that normal?
Apparently taking R61 out of the equation kills FM Muting.
That would be true. The FM muting signal based on signal strength comes through TR06. Lifting R61 tells us the seemingly full time muting is coming through TR07 question is why.
Is TR07 bad, or is the voltage at pin 21 not doing what it should, or is the problem coming through TR06? You could put R61 back and lift R59.
Either I busted R59 or it was already busted. Scheme says it's 100K I believe, but what I took off the board looks like 3 oranges and a brown or gold.
So 3330 ohms?
If I test it I get 36K ohms.
So 3330 ohms?
If I test it I get 36K ohms.
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It plays fine w/o R59, but again no muting.
Also, I test pin 9 on HA1196 and it was 0 V. Block diagram shows it going to the Stereo lamp, which is not coming on.
Also, I test pin 9 on HA1196 and it was 0 V. Block diagram shows it going to the Stereo lamp, which is not coming on.
Not sure what to make of that. Both the non DB and the Db manuals call it a 100k. It does not look like a typical Sansusi resistor either. (one of these things is not like the other)
Do you recall if the solder joints looked original?
It is most likely a gold tolerance band, making it a 33k resistor. Take a look at R56 it should be a 100k.
Is that with R61 put back and just R59 removed? I would put a 100k back for R59.
For the stereo lamp check for + 6 volts at pin 24. If you don't have it then either the bulb is bad or the power supply feeding it is not working.
If you have +DC voltage at pin 24 then shorting pins 23 to pin 24 should make the lamp come on. There is a transistor switch between the IC and the lamp.
If the lamp is good, mark the position of VR04 and try rocking it back and forth a little to see if the lamp lights.
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Put R61 back before I pulled R59 and it played fine. Think I must have broken R59.
Pretty sure everything is factory/original. There are at least a dozen of these type resistors with the flat ends on the board. I found another with the same bands and it measured 25k in circuit, but I think you’re right and it’s 33k.
EDIT: Photo to show the funky resistors.
Pretty sure everything is factory/original. There are at least a dozen of these type resistors with the flat ends on the board. I found another with the same bands and it measured 25k in circuit, but I think you’re right and it’s 33k.
EDIT: Photo to show the funky resistors.
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Are you going to do the dial mod? Where the dial lights stay on even when you select Aux or Phone? The creator of the new selector switch thinks the new switch will handle that mod, but he wants to confirm it. If you do the dial mod please post the result.
Think the resistor I put in to get Vs going to the front end is the only new resistor.
R56 is 100k ohms.
Put 100k ohms in for R59, tuner‘s very quiet again.
0 volts at pin 24.
Must have had a bad connection to pin 24.
Measured the E of TR09 and got 8.46 Vdc, so went back to pin 24 and got the same. Base of TR09 is 7.88 Vdc and it goes through at that voltage to pin 9 in HA1196.
Also, no idea why, but FM is now playing at normal levels with all resistors connected! AND FM MUTING WORKS!!!!!!
An electron miracle!?
Measured the E of TR09 and got 8.46 Vdc, so went back to pin 24 and got the same. Base of TR09 is 7.88 Vdc and it goes through at that voltage to pin 9 in HA1196.
Also, no idea why, but FM is now playing at normal levels with all resistors connected!
AND FM MUTING WORKS!!!!!!An electron miracle!?
Didn’t last long. Back to low volume mode.
The muting circuit has it's own IF amp, TR04. Diode D08 rectifies the 70Mhz giving a varying DC level based on signal strength. That DC goes through VR03 to the base of TR05 turning it on or off based on the level. You can monitor the base voltage at TR05 to see what kind of levels you see when tuning. You can also monitor the collector of TR05 to see if it turning on & off.
You could have a bad IF amp IC which would give low levels. And typically even if one has failed it will still pass a signal.
I don't know what the typical levels would be. I have used a scope in the past to step through the IF strip looking for increased levels after each amp stage.
Could be a crappy transistor, carbon comp resistors that have drifted way out, IF amp IC, even a bad IF transformer (bad transformers are soemwhat rare)
Heck it could be that somebody has been twisting and turning pots and transformer cores.
You could have a bad IF amp IC which would give low levels. And typically even if one has failed it will still pass a signal.
I don't know what the typical levels would be. I have used a scope in the past to step through the IF strip looking for increased levels after each amp stage.
Could be a crappy transistor, carbon comp resistors that have drifted way out, IF amp IC, even a bad IF transformer (bad transformers are soemwhat rare)
Heck it could be that somebody has been twisting and turning pots and transformer cores.
Weirdness with the FM Muting switch caused me to clean the switch again and reflow the solder on that board.
I had it turned up so I could actually hear some FM and pushed the muting button to "off", and it went to normal volume, AS IN REALLY LOUD!
Previously pushing muting to off made no difference, there wasn't any muting at all and the volume level didn't change. Now turning muting on cut the levels again and turning it off gave normal volume. So I figured it was time to try tweaking the muting VR (3) to see if muting was just set too high, and shazam! Normal volume AND the Stereo lamp lit.
Gonna do the DC offset and bias and run it for a day
Muchas gracias Matt!
I had it turned up so I could actually hear some FM and pushed the muting button to "off", and it went to normal volume, AS IN REALLY LOUD!
Previously pushing muting to off made no difference, there wasn't any muting at all and the volume level didn't change. Now turning muting on cut the levels again and turning it off gave normal volume. So I figured it was time to try tweaking the muting VR (3) to see if muting was just set too high, and shazam! Normal volume AND the Stereo lamp lit.
Gonna do the DC offset and bias and run it for a day
Muchas gracias Matt!
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The SS and tuning had been acting normal the whole time.